Antibodies, peptides, and enzymes are often used as molecular recognition elements in chemical and biological sensors. However, their lack of stability and signal transduction mechanisms limits their use as sensing devices. Recent advances in the field of molecularly imprinted polymers (MIPs) have created synthetic materials that can mimic the function of biological receptors but with less stability constraints. These polymers can provide high sensitivity and selectivity while maintaining excellent thermal and mechanical stability. To further enhance the advantages of the traditional imprinted polymer approach, an additional fluorescent component has been introduced into these polymers. Such a component provides enhanced chemical affinity as well as a method for signal transduction. In this type of imprinted polymer, binding of the target analyte invokes a specific spectral signature from the reporter molecule. Previous work has provided molecularly imprinted polymers that are selective for the hydrolysis products of organophosphorus species such as the nerve agents sarin and soman. (A. L. Jenkins, O. M. Uy and G. M. Murray, Anal. Chem., 1999, 71, 373). In this paper the direct imprinting of non-hydrolyzed organophosphates including pesticides and insecticides is described. Detection limits for these newly developed MIP sensors are less than 10 parts per trillion (ppt) with long linear dynamic ranges (ppt to ppm) and response times of less than 15 min.

A detailed investigation of phonon modes in DNA macromolecules is presented. This work presents experimental evidence to confirm the presence of multiple dielectric resonances in the submillimeter-wave spectra (i.e., approximately 0.01-10 THz) obtained from DNA samples. These long-wave (i.e., approximately 1-30 cm(-1)) absorption features are shown to be intrinsic properties of the particular DNA sequence under study. Most importantly, a direct comparison of spectra between different DNA samples reveals a large number of modes and a reasonable level of sequence-specific uniqueness. This work establishes the initial foundation for the future use of submillimeter-wave spectroscopy in the identification and characterization of DNA macromolecules.

Raman spectroscopy is being evaluated as a candidate technology for waterborne pathogen detection. We have investigated the impact of key experimental and background interference parameters on the bacterial species level identification performance of Raman detection. These parameters include laser-induced photodamage threshold, composition of water matrix, and organism aging in water. The laser-induced photodamage may be minimized by operating a 532 nm continuous wave laser excitation at laser power densities below 2300 W/cm(2) for Grampositive Bacillus atrophaeus (formerly Bacillus globigii, BG) vegetative cells, 2800 W/cm(2) for BG spores, and 3500 W/cm(2) for Gram-negative E. coli (EC) organisms. In general, Bacillus spore microorganism preparations may be irradiated with higher laser power densities than the equivalent Bacillus vegetative preparations. In order to evaluate the impact of background interference and organism aging, we selected a biomaterials set comprising Gram-positive (anthrax simulants) organisms, Gram-negative (plague simulant) organisms, and proteins (toxin simulants) and constructed a Raman signature classifier that identifies at the species level. Subsequently, we evaluated the impact of tap water and storage time in water (aging) on the classifier performance when characterizing B. thuringiensis spores, BG spores, and EC cell preparations. In general, the measured Raman signatures of biological organisms exhibited minimal spectral variability with respect to the age of a resting suspension and water matrix composition. The observed signature variability did not substantially degrade discrimination performance at the genus and species levels. In addition, Raman chemical imaging spectroscopy was used to distinguish a mixture of BG spores and EC cells at the single cell level.

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